喜歡就充值下載吧。。。資源目錄里展示的全都有，，下載后全都有，所見即所得，CAD圖紙均為高清圖可自行編輯，文檔WORD都可以自己編輯的哦，有疑問咨詢QQ:1064457796,,,課題后的【XX系列】為整理分類用，與內(nèi)容無關(guān)，請忽視

油氣彈簧特性建模與仿真 1、文獻(xiàn)查閱的方法 (1) 國家數(shù)字圖書館（CNKI）中的全國期刊數(shù)據(jù)庫 (2) 國家數(shù)字圖書館（CNKI）全國優(yōu)秀博碩士論文數(shù)據(jù)庫中 (3) 互聯(lián)網(wǎng)檢索 2、國內(nèi)外研究歷史與現(xiàn)狀 在國外油氣懸架系統(tǒng)的研究已經(jīng)開展的比較全面了，無論從理論上還是應(yīng)用上都取得了一些成果。學(xué)者們對油氣彈簧的結(jié)構(gòu)和性能進(jìn)行了大量的理論分析和定性定量的研究，目前主動懸架的應(yīng)用已經(jīng)起步，并且研發(fā)了一些利用主動懸架控制的產(chǎn)品。當(dāng)前對油氣懸架的研究內(nèi)容主要在于： (1) 建立油氣彈簧合理的非線性數(shù)學(xué)模型 大量信息表明，目前建立非線性數(shù)學(xué)模型的方式基本可以分為兩種，即參數(shù)化和非參數(shù)化。參數(shù)化方法建立的模型依據(jù)的是油氣彈簧內(nèi)部的結(jié)構(gòu)參數(shù)和相關(guān)的物理定律，它能夠較為精確地描述其內(nèi)部工作狀態(tài)，清晰地分析各因素對系統(tǒng)的影響；并且每個參數(shù)都有明確的物理意義，適合于油氣彈簧缸自身特性的研究，但也存在參數(shù)多，計(jì)算速度慢、校準(zhǔn)時間長等缺點(diǎn)。而非參數(shù)化模型的建立通常需要大量的試驗(yàn)，是通過試驗(yàn)數(shù)據(jù)擬合來描述油氣彈簧的非線性特性的，彌補(bǔ)了參數(shù)化方法的缺點(diǎn)，但卻耗資巨大。綜合其各自特點(diǎn)和局限性，參數(shù)化相對于非參數(shù)化設(shè)計(jì)更具有優(yōu)勢。 (2) 開發(fā)新型結(jié)構(gòu)形式的油氣懸架和研究主動控制策略 國內(nèi)學(xué)者對油氣懸架的研究，主要是油氣懸架的剛度特性和阻尼特性的非線性特性，通過建模定性分析、仿真及對整車行駛平順性能的評價指標(biāo)分析。主要采用的軟件工具是 MATLAB/SIMULINK 模塊，如設(shè)計(jì)平衡懸架系統(tǒng)來實(shí)現(xiàn)整車剛度可變，從而改善車身傾側(cè)性能。但是多數(shù)研究缺乏定性和定量的分析、試驗(yàn)和對油氣懸架模型的修正。雖然建立了油氣懸架的柔性力學(xué)模型和振動模型，并通過有限元分析軟件進(jìn)行了一些靜力學(xué)和動力學(xué)分析，對懸架結(jié)構(gòu)進(jìn)行了初步的優(yōu)化設(shè)計(jì)，但還處于研究階段，推廣使用較少。從總體上看， 國內(nèi)在油氣懸架技術(shù)研究方面主要集中在原理介紹、物理模型、數(shù)學(xué)建模、計(jì)算機(jī)仿真分析上，目前還沒有形成一套系統(tǒng)的、完善的、切實(shí)可靠的方法和理論用于指導(dǎo)油氣懸架的設(shè)計(jì)，仍然處于與國外樣機(jī)類比、參考設(shè)計(jì)、試驗(yàn)修改模型的階段。 3、對已掌握文獻(xiàn)的綜述與分析 ⅰ油氣懸架種類 如圖 2.1 為單氣室油氣懸架結(jié)構(gòu)原理圖在活塞桿的內(nèi)部有一個空腔，該腔通過數(shù)個阻尼孔和單向閥將液壓缸的大、小腔（A、B 腔）溝通，蓄能器通過管路與液壓缸的大腔相通。當(dāng)車輛受到不平路面激勵時，活塞及活塞桿組件會相對于缸筒作往復(fù)運(yùn)動，若活塞及活塞桿相對缸筒收縮，則 A 腔的油液受到壓縮而向兩個方向移動：一是進(jìn)一步壓縮蓄能器內(nèi)部的氣體而進(jìn)入蓄能器；二是通過阻尼孔和單向閥而進(jìn)入 B腔。若活塞及活塞桿相對缸筒伸張，則 B 腔的油液受到壓縮，迫使 B 腔的油液通過阻尼孔向 A 腔流動（此時單向閥處于關(guān)閉狀態(tài)），同時因 A 腔增大的體積大于 B 腔縮小的體積，結(jié)果會導(dǎo)致蓄能器的部分油液在氣體壓力作用下進(jìn)入 A 腔。 在前一種情形下，因單向閥開啟，活塞及活塞桿組件相對缸筒運(yùn)動時受到的阻尼力較小，這相當(dāng)于傳統(tǒng)懸架中的彈簧作用；在后一種情形下，因單向閥關(guān)閉，活塞及活塞桿組件相對缸筒運(yùn)動時受到的阻尼力較大，這相當(dāng)于傳統(tǒng)懸架中的減振器作用。 圖 2.2 所示的是帶反壓氣室的雙氣室懸架液壓缸結(jié)構(gòu)，液壓缸的內(nèi)部有 A、B、C 三個油腔，C 腔一方面通過數(shù)個阻尼孔和單向閥與 B腔相通，另一方面還通過管路與左蓄能器（反壓氣室）相通，A 腔通過管路僅與右蓄能器（主氣室）相通。當(dāng)活塞及活塞桿相對缸筒收縮時，A 腔的油液會受到壓縮而進(jìn)入右蓄能器，使主氣室內(nèi)的氣壓增高彈簧的剛度增大，C腔的油液因 B 腔容積增大而受到左蓄能器氣體壓縮進(jìn)而通過阻尼孔和單向閥進(jìn)入 B 腔，而反壓氣室內(nèi)的氣壓下降；相反地當(dāng)活塞及活塞桿相對缸筒伸張時，主氣室內(nèi)的氣壓降低，B 腔的油液因受到壓縮而通過阻尼孔進(jìn)入左蓄能器，右蓄能器的油液因 A 腔容積增大而受到右蓄能器氣體壓縮進(jìn)而進(jìn)入 A 腔，使反壓氣室內(nèi)的氣壓增高。由于反壓氣室的作用，使懸架在伸張行程時的剛度比單氣室懸架的剛度要大得多。只要對兩氣室氣壓和容積參數(shù)選擇適當(dāng)，就可以使懸架剛度保持合適的變化規(guī)律，使懸架具有較理想的彈性特性。 圖2.3 所示兩級壓力式油氣懸架其結(jié)構(gòu)原理。它的特點(diǎn)是在工作活塞上部設(shè)有兩個并列氣室，但兩個氣室工作壓力不同。其中之一稱為主氣室 A，充有氣壓與正常單氣室油氣懸架相近的氮?dú)?；另一氣室稱為補(bǔ)償氣室 B，其中充有比主氣室氣壓高的氮?dú)?。兩個氣室都用橡膠隔膜將氣體與油液隔開。兩個氣室的作用就像鋼板彈簧中主簧與副簧的作用一樣。由于懸架中的補(bǔ)償氣室氣壓高于主氣室的氣壓，因此，當(dāng)懸架上載荷增加時，先是主氣室參加工作。當(dāng)載荷增加到一定程度時，補(bǔ)償氣室才參加工作。把補(bǔ)償氣室開始工作時的懸架載荷稱為臨界載荷，當(dāng)懸架上載荷超過臨界載荷時，補(bǔ)償氣室和主氣室一起工作。雙級壓力式油氣懸架由于兩個氣室不是同時參加工作，而是根據(jù)汽車載荷的變化先后參加工作，因而使懸架剛度的變化更加符合懸架性能的要求，從而保證汽車空載與滿載時懸架有大致相等的固有振動頻率，從而提高了汽車行駛的平順性。 ⅱ油氣懸架特性 (1)非線性剛度 傳統(tǒng)車輛懸架一般是以鋼板彈簧和阻尼元件為主的被動懸掛，其剛度特性是線性的或分段線性的，因此其剛度基本保持不變；而油氣懸架的彈性介質(zhì)是惰性氣體，其剛度特性是非線性的、可以隨外界的激勵變化而調(diào)整的。車輛在良好的路面上行駛時動行程小，懸架剛度小，通過對彈簧性系數(shù)的調(diào)整，來改善汽車的乘坐舒適性與操縱穩(wěn)定性，從而保證車輛良好的行駛平順性；車輛在起伏路面上行駛時，懸架剛度大，能吸收較多的沖擊能量，避免路面對車輛的剛性沖擊，且能使車身獲得很低的自由振動頻率，實(shí)現(xiàn)頻率衰減，從而使車輛具有良好的穩(wěn)定性。這就滿足了車輛行駛時的平順性，同時能夠吸收較多的沖擊能量使車輛在劣質(zhì)路面上也能保持一定的行駛速度。 (2)非線性阻尼 阻尼特性主要與車架相對于車橋的速度有關(guān)，調(diào)整減振器阻尼系數(shù)，可迅速地減小或抑制車架的振動，防止汽車急速起步或急加速時車尾下蹲；防止緊急制動時的車頭下沉；防止汽車急轉(zhuǎn)彎時車身橫向搖動；防止汽車換擋時車身縱向搖動等，提高行駛平順性和操縱穩(wěn)定性，具有很好的減振性。 (3)車身高度自由調(diào)節(jié) 無論車輛的負(fù)載多少，都可以保持汽車高度一定，車身保持水平，從而使前大燈光束方向保持不變；當(dāng)汽車在壞路面上行駛時，可以使車高升高，防止車橋與路面相碰；當(dāng)汽車高速行駛時，又可以使車高降低，以便減少空氣阻力，提高操縱穩(wěn)定性。這對改善車輛的行駛性能十分重要。 (4)懸架閉鎖功能 由于油液壓縮性較小，當(dāng)將油氣懸架的液壓缸與蓄能器分置，并切斷它們及其它液壓元件的連接油路，即可實(shí)現(xiàn)油氣懸架剛性閉鎖狀態(tài)。在這種條件下，可以減輕或消除車輛的振動，使車輛可承受較大載荷并能緩慢移動。這對實(shí)現(xiàn)起重機(jī)吊裝物品移動就位、坦克發(fā)射炮彈這樣的特殊工況是很有意義的。 (5)蓄能器儲能大 油氣彈簧的單位儲能比為 3.3 ×105Nm/Kg(在 6MPa 氮?dú)獬錃鈮毫ο?，而鋼板彈簧的單位儲能比為 76～115 Nm/Kg，扭桿彈簧的單位儲能比為 254～380 Nm/Kg，橡膠彈簧的單位儲能比為 508～1016 Nm/Kg，圓柱螺旋彈簧的單位儲能比為 178～280 Nm/Kg，有利于減輕懸架重量和減小結(jié)構(gòu)尺寸。同時油氣懸架體積小、重量輕且減輕了非懸掛質(zhì)量，用于重型車輛，比鋼板懸架輕50％以上，比扭桿彈簧輕 20％左右；對于重型車輛來說，這一特點(diǎn)可以有效地減輕懸架重量和減小結(jié)構(gòu)尺寸。 (6)結(jié)構(gòu)緊湊、易于布置 油氣懸架的懸架缸沒有專用的減振器，而是把減振器功能融于懸架缸內(nèi)。加裝阻尼閥之后，通常用浮動活塞將油氣分離，更適應(yīng)重型越野車輛遠(yuǎn)距離行程的特點(diǎn)。同時，油氣彈簧系統(tǒng)體積小，連接簡單，便于拆裝。 (7)通用性好 油氣懸架只需少數(shù)幾種不同直徑的懸架缸，匹配不同的蓄能器初始充氣壓力和充油量就可在不同負(fù)載的車輛上應(yīng)用，易于產(chǎn)品系列化。 油氣懸架也有不足之處： a.油氣懸架布置在車外，防護(hù)性較差。 b.成本一般較扭桿懸架要高，油氣懸架除了需要設(shè)置彈簧缸和蓄能器外，還需要配置液壓控制閥、阻尼孔、液壓泵、油箱以及濾清器等輔件，因而成本較高。 c.油氣懸架壓力較高，對油和氣的密封裝置要求較高，零部件加工精度要求較嚴(yán)，否則會因漏油、漏氣而不能使用。 d.油氣懸架一般較難在-40 度的氣溫下正常工作，它對油液和橡膠的低溫性能要求較高。 ⅲ研究油氣彈簧亟待解決的問題 從油氣懸架的發(fā)展現(xiàn)狀可以看出，國外已經(jīng)到達(dá)應(yīng)用階段，而國內(nèi)還處于理論研究，試驗(yàn)修正階段，差距很大，需要做如下幾方面的努力 (1)系統(tǒng)性、基礎(chǔ)性研究。這需要增加研究、開發(fā)經(jīng)費(fèi)，引進(jìn)和設(shè)計(jì)試驗(yàn)設(shè)備。高?？梢越柚髽I(yè)試驗(yàn)平臺，既進(jìn)行了油氣懸架理論研究、仿真分析，同時又研究了油氣懸架具體結(jié)構(gòu)設(shè)計(jì)，開發(fā)出獨(dú)立自主的油氣懸架產(chǎn)品。 (2)加強(qiáng)結(jié)構(gòu)設(shè)計(jì)和優(yōu)化設(shè)計(jì)。研究油氣懸架的剛度特性、阻尼特性、頻率特性，減振效果等，進(jìn)行定性定量說明。油氣懸架的優(yōu)化設(shè)計(jì)，它不是單純地油氣懸架參數(shù)的優(yōu)化，還包括不同的油氣懸架結(jié)構(gòu)性能差異的對比以及影響車輛各種性能的因素，并將優(yōu)化結(jié)果納入油氣懸架的設(shè)計(jì)中，從而大幅度改善和提高車輛性能。 (3)規(guī)范研究設(shè)計(jì)規(guī)則。由于油氣懸架系統(tǒng)性、基礎(chǔ)性研究已經(jīng)逐步加強(qiáng)，理論研究、實(shí)際設(shè)計(jì)相結(jié)合模式也在不斷的深入，所以需要建立一套通用的油氣懸架設(shè)計(jì)規(guī)則，使對油氣懸架的研究設(shè)計(jì)更加規(guī)范化、系列化。 (4)研制、開發(fā)整車和多橋油氣懸架系統(tǒng)虛擬樣機(jī)，實(shí)現(xiàn)懸架系統(tǒng)的參數(shù)化、可視化設(shè)計(jì)，并針對油氣懸架系統(tǒng)開發(fā)專門的計(jì)算機(jī)仿真軟件。 (5)從被動懸架技術(shù)向半主動懸架、主動懸架技術(shù)發(fā)展，選擇微處理器系統(tǒng)，采用電子自動化控制，最終實(shí)現(xiàn)油氣懸架的主動化自適應(yīng)智能控制系統(tǒng)。油氣懸架系統(tǒng)是一種新型的底盤懸掛系統(tǒng)，是空氣懸架的應(yīng)用特例。隨著技術(shù)的進(jìn)步，關(guān)鍵參數(shù)的設(shè)定已被掌握，油氣懸架系統(tǒng)以現(xiàn)代機(jī)械制造技術(shù)為依據(jù)，結(jié)構(gòu)和性能在逐漸地改進(jìn)和完善。油氣懸架系統(tǒng)在國內(nèi)車輛底盤技術(shù)上的需求也在不斷地增大，應(yīng)用前景非常廣闊。 4、參考文獻(xiàn) [1] 封士彩，王國彪.工程車輛油氣懸架的現(xiàn)狀與發(fā)展[J].礦山機(jī)械.2000, 12,32-33. [2] 耿景榮, 帶反壓氣室的油氣彈簧理論建模和結(jié)構(gòu)設(shè)計(jì). TH122 [3] 周長城,袁光明，疊加閥片式油氣彈簧節(jié)流縫隙設(shè)計(jì)及特性試驗(yàn). U463.33 [4] 周長城,張紹閣,顧亮,環(huán)形彈性閥片彎曲變形曲面方程及其解. 2006年7月 [5] 陳軼杰,李彪,雷強(qiáng)順,王亞軍. 基于阻尼閥參數(shù)的油氣彈簧示功特性分析2009,11 [6] 周長城.開閥速度對油氣彈簧閥系設(shè)計(jì)參數(shù)的影響.2008,2 [7] 李春艷,謝東升.論油氣懸掛的性能特點(diǎn)及研究現(xiàn)狀. [8] 黃郁馨, 陳軼杰, 王亞軍.油氣彈簧彈性力值解析計(jì)算與仿真分析. 2009年第6期 [9] 周長城,石沛林. 油氣彈簧疊加閥片應(yīng)力分析. 2008年(第30卷)第4期 [10] 陳軼杰,潘云杰,白國忠. 油氣彈簧閥片均布載荷變形研究與數(shù)學(xué)建模. 2010年6月 [11] 陳軼杰, 顧亮, 管繼富. 油氣彈簧縫隙節(jié)流分析與數(shù)學(xué)模型研究. 2008年5月 [12] 陳軼杰,顧亮. 油氣彈簧環(huán)形節(jié)流閥片大撓曲變形分析與試驗(yàn). 2009年3月 [13] 周長城,鄭志蘊(yùn). 油氣彈簧阻力特性計(jì)算機(jī)仿真. 2006年8月 [14] 陳志林,金達(dá)峰,趙六奇,馬國新. 油氣主動懸架非線性模型的建立仿真與試驗(yàn)驗(yàn)證. [15] 孫文君.汽車油氣彈簧特性仿真研究.2009,12 [16] 莊德軍，柳江，喻凡，林逸. 汽車油氣彈簧非線性數(shù)學(xué)模型及特性. 2005年9月 Modeling and simulation of oil and gas spring characteristics 1, the method of consulting literature materials (1) the national digital library in national journals database (CNKI) (2) the national digital library (CNKI) national excellent bo master thesis database (3) the Internet search 2, research history and present situation at home and abroad In foreign oil and gas suspension system has carried out the study of comprehensive, whether in theory or application results have been achieved. Scholars on the structure and properties of oil and gas spring for a lot of theoretical analysis and qualitative research, quantitative at present the application of active suspension has been started, and developed some products use active suspension control. The current study of oil and gas suspension content mainly lies in: (1) to establish a nonlinear mathematical model of hydro-pneumatic spring reasonable Large amounts of information indicated that the way to establish the mathematical model of nonlinear basic can be divided into two kinds, namely the parametric and nonparametric. Parametric method to establish the internal structural parameters of the model is based on oil and gas spring and related laws of physics, it can more accurately describe the internal working condition, the analysis of the effect of various factors on the system clearly; And each parameter has a clear physical meaning and is suitable for oil and gas spring cylinder's own characteristics, but there are many parameters, calculation speed is slow, shortcomings and so on calibration time is long. Rather than a parameterized model usually need a lot of experiments, is through the test data fitting to describe the nonlinear characteristics of the oil and gas spring, make up for the shortcomings of the parametric method, but it is expensive. Integrated the characteristics and limitations, parameterized more advantages relative to the parametric design. (2) developing new structure form of oil and gas suspension and study the active control strategy Domestic scholars on the study of oil and gas suspension, mainly oil and gas suspension stiffness and damping characteristics of nonlinear characteristic, through qualitative analysis, simulation modeling and analysis of the evaluation index of vehicle ride performance. Mainly is the MATLAB/SIMULINK software tools used modules, such as design balanced suspension system for vehicle variable stiffness, improve body heeling performance. But most research lack of qualitative and quantitative analysis, test and the model of hydro-pneumatic suspension is corrected. Although the flexible mechanics model of hydro-pneumatic suspension is established and the vibration model, and through the finite element analysis software of statics and dynamics analysis, the optimization of suspension structure has carried on the preliminary design, but are still in research stage, promote the use of less. Overall, Domestic in oil and gas suspension technology research mainly focused on the principle, physical model, mathematical modeling and computer simulation analysis, has not formed a set of system, perfect, practical and reliable method and theory to guide the design of the oil and gas suspension, is still in the home and abroad analogy, reference design and test phase of modified model. 3, to grasp the literature review and analysis I type hydro-pneumatic suspension As shown in figure 2.1 for A single chamber oil-gas suspension structure schematic diagram on the inside of the piston rod has A cavity, the cavity through A number of damping holes and one-way valve to hydraulic cylinder of the large and small cavity (A, B) communication, accumulator by pipe and hydraulic cylinder's big cavity are interlinked. When vehicles are motivated by the uneven road surface, piston and piston rod components will be relative to the cylinder for reciprocating motion, if the relative cylinder piston and piston rod contraction, then A cavity of the oil by compression and move in two directions: one is further compressed gas into the accumulator within the accumulator; Second, through the damping hole and check valve into the B cavity. If relative cylinder piston and piston rod stretching, the cavity of the oil by compression, B forced B cavity fluid flow through damping hole into A chamber (one-way valve closed at this time), at the same time due to increase the volume of the cavity is greater than B cavity to reduce the volume, the result causes accumulator part of the oil into A cavity in under the action of gas pressure. In the former case, because the one-way valve open, piston and piston rod movement or relative cylinder components of damping force is small, this is equivalent to the spring function of traditional suspension; In the latter case, because the check valve closed, piston and piston rod movement or relative cylinder components of damping force is bigger, this is equivalent to the traditional suspension shock absorber role. Is shown in figure 2.2 with the compressed air chamber of the double chamber suspension hydraulic cylinder structure, the hydraulic cylinder has A, B, C three oil cavity, the cavity C on the one hand, through A number of damping holes and one-way valve and B cavity are interlinked, on the other hand also through the line and left accumulator (anti air chamber) are interlinked, A cavity through the line and just right accumulator (main chamber) is same. When the piston and piston rod relative cylinder contraction, A cavity of the oil will be compressed and into the right accumulator, make the main gas increases higher indoor air spring stiffness, C cavity oil by increasing B cavity volume from left accumulator gas compression, in turn, B through damping hole and check valve into the cavity, and the air indoor air pressure drop; On the contrary, when relative cylinder piston and piston rod for the main indoor air pressure reducing gas, B cavity oil by compression and through damping hole into the left accumulator, right accumulator of oil gas accumulator right by increasing A cavity volume compression, in turn, into A cavity, the increased pressure of compressed air indoor. Due to the role of the air chamber, the stiffness of suspension in stretching the trip than single chamber suspension stiffness is much larger. As long as the two air chamber pressure and volume choosing appropriate parameters, can keep the suspension stiffness of the changing rule of the right, make the suspension with ideal elastic properties. A two-stage pressure type is shown in figure 2.3 the structure principle of hydro-pneumatic suspension. Its characteristic is in upper pistons work has two parallel air chamber, but two different air chamber pressure. One of them said that as the main air chamber A, filled with air pressure and normal single chamber of hydro-pneumatic suspension nitrogen; In another room called compensation chamber B, in which the charge is higher than the main chamber pressure of nitrogen. Both air chamber with a rubber diaphragm to separate gas and oil. The role of two air chamber is similar to the main spring leaf spring and the function of each pair of spring. Due to the suspension of the compensation chamber air pressure is higher than the main chamber, therefore, when the suspension load increases, the first main air chamber to participate in the work. When the load increases to a certain degree, compensation chamber to attend work. The compensation chamber start work when the suspension load is called the critical load, when the suspension load exceeds the critical load, compensation chamber and the main chamber to work together. Two-stage pressure type oil and gas suspension for two air chamber is not a job at the same time, it has to work according to the variation of vehicle load, so that the suspension stiffness change more accord with the requirement of suspension performance, to ensure that when the car no-load and load suspension have roughly equal natural vibration frequency, so as to improve the ride comfort of the car. Ii suspension characteristics of oil and gas (1) nonlinear stiffness Tradition vehicle suspension of leaf spring and damping element on the passive suspension, its stiffness is linear or piecewise linear features, so its rigidity basic remain unchanged; And the elastic medium of hydro-pneumatic suspension is the inert gas, its stiffness characteristics is non-linear and can change with the external incentive and adjustment. When vehicles are driven in good pavement dynamic small stroke, suspension stiffness is small, through the spring coefficient of the adjustment, to improve vehicle ride comfort and handling stability, thus ensuring the vehicle ride comfort; good When vehicles are driven on the ups and downs road, suspension stiffness big, can absorb more impact energy, avoid rigid pavement of vehicle impact, and can make the body get free vibration frequency of low implementation frequency attenuation, so that the vehicle has a good stability. It can meet the vehicle ride comfort, at the same time to absorb more impact energy in inferior the vehicle road can maintain a certain speed. (2) the nonlinear damping Damping characteristics are mainly related to the speed of the frame relative to the axle, adjusting the shock absorber damping coefficient, can quickly reduce or suppress the vibration of the frame, prevent rapid start-up or urgent acceleration when the rear of the squat; To prevent emergency brake the car when sinking; Prevent body lateral shake when the car turn; To prevent car body such as longitudinal shake when shifting, improve riding comfort and handling stability, has the very good vibration reduction. (3) the free height adjustment for the body , no matter how much the load of the vehicle can keep the car must be, body level, thus make headlights beam direction remains the same; When the cars are driven on the bad road, can make the car high rise, to prevent the axle into the road; When the car speeding, and can lower the car is high, in order to reduce the air resistance, improve the handling stability. It would be very important to improve the motion of the vehicle performance. (4) suspension locking function Due to the small oil compressibility, when the oil and gas suspension hydraulic cylinder and accumulator division, and cut off their oil, and other hydraulic components connected rigid closed hydro-pneumatic suspension can be realized. Under these conditions, can reduce or eliminate the vibration of the vehicle, the vehicle is under high load and can be to move slowly. The realization of crane hoisting objects move in place, the tank artillery such special condition, it is very meaningful. (5) the accumulator energy storage Unit hydro-pneumatic spring energy storage ratio 3.3 x 105 Nm/Kg (in 6 mpa nitrogen gas pressure), and the unit of leaf spring energy storage ratio of 76 ~ 115 Nm/Kg, the unit of torsion bar spring energy storage ratio of 254 ~ 380 Nm/Kg, the unit of rubber spring energy storage ratio of 508 ~ 1016 Nm/Kg, the unit of cylindrical helical spring energy storage ratio of 178 ~ 280 Nm/Kg, is helpful to reduce suspension weight and decrease the size of the structure. Hydro-pneumatic suspension is at the same time, small volume, light weight and reduce the quality of the suspension, used for heavy vehicles, lighter than the steel suspension of more than 50%, about 20% lighter than the torsion bar spring; For heavy vehicles, this characteristic can effectively reduce the suspension weight and decrease the size of the structure. (6) compact structure, easy to decorate The suspension of hydro-pneumatic suspension cylinder without special shock absorber, but the function into suspension shock absorber in cylinder. After adding damping valve, usually with a floating piston oil and gas separation, more adapt to the characteristics of the heavy off-road vehicles long-distance travel. At the same time, the oil and gas spring system is small in size, simple connection, convenient for dismantling. (7) good commonality Only a handful of hydro-pneumatic suspension is the suspension of different diameter cylinder, matching of different initial charge pressure of accumulator and oil charge amount can be applied on different load of vehicles, easy to product seriation. Oil and gas suspension has the defects of his: A. layout of hydro-pneumatic suspension is outside the car, less protection. B. cost is generally torsion bar suspension, in addition to the need to set the spring hydro-pneumatic suspension cylinder and the accumulator, also need to configure the hydraulic control valve, damping hole, hydraulic pump, tank and filter accessaries, thus higher cost. C. suspension of oil and gas pressure is higher, the oil and gas sealing device of the demand is higher, more strict precision parts processing, otherwise cannot be used for oil leakage, leakage. D. generally difficult to hydro-pneumatic suspension under - the temperature of 40 degrees to work properly, it is of high oil and low temperature performance of rubber. Iii research problem urgently to be solved in oil and gas spring Can be seen from the development of oil and gas suspension, abroad has reached the application stage, and the country is still in the theoretical research, experimental correction phase, the difference is very big, need to do the following several aspects (1) the systemic and basic research. This need to increase the research and development funds, the introduction of test equipment and design. Colleges and universities can use enterprise test platform, both the oil and gas suspension theory research, the simulation analysis, and studied the concrete structure design of hydro-pneumatic suspension at the same time, to develop independent suspension of oil and gas products. (2) to strengthen the structure design and optimization design. Study of hydro-pneumatic suspension stiffness, damping characteristics, frequency characteristics, anti-vibration effect, etc., qualitative quantitative description. Optimization design of hydro-pneumatic suspension, it is not simply the oil and gas suspension parameters optimization, including comparison of different oil and gas suspension structure performance differences as well as the factors affecting the performance of vehicle, and the optimized results included in the design of oil and gas suspension, which significantly improve and enhance vehicle performance. (3) the normative research design rules. Due to oil and gas suspension system, basic research has gradually strengthened, combination of theoretical research and practical design model has been further, so you need to establish a set of general rules of oil and gas suspension design, make the study of oil and gas suspension design is more standardization, seriation. (4) the development, the development of hydro-pneumatic suspension vehicle and bridge system virtual prototype, the parameters of suspension system, visual des